Esterified ephedrine derivatives with prolonged antiulcer activity

ABSTRACT

Esterified ephedrine derivatives with prolonged antiulcer activity and low toxicity, having the following general formula: ##STR1## in which R is: ##STR2## The invention also describes a process for preparing derivatives of formula (I) and compositions containing them as active principle.

This application is a Rule 60 Divisional Application of Ser. No.07/254,220, filed Oct. 6, 1988, now U.S. Pat. No. 4,935,444.

1. Field of the invention

This invention relates to esterified ephedrine derivatives withprolonged antiulcer activity and low toxicity.

2. Description of the prior art

Non-esterified ephedrine derivatives are known possessing antiulceractivity.

In particular, the compound WAS 4304 of European patent application No.84108424.7 demonstrates very interesting antiulcer activity whenadministered intraperitoneally in experimental tests; however its LD₅₀for this administration method is very low (115 mg/kg) and in additionits activity is of very limited duration.

SUMMARY OF THE INVENTION

We have now discovered esterified ephedrine derivatives which besidespossessing high antiulcer activity have a lower toxicity and a moreprolonged action than the compound WAS 4304 of the prior art.

The derivatives according to the present invention have the followinggeneral formula: ##STR3## in which R is: ##STR4## The invention alsorelates to a process for preparing the derivatives of general formula(I) and to the pharmaceutical compositions of antiulcer activity whichcontain at least one derivative of general formula (I) as activeprinciple and a therapeutically acceptable carrier.

DETAILED DESCRIPTION OF THE INVENTION

The process for preparing the derivatives (I) of the present inventionis implemented by the following stages:

(a) reacting the acid RCOOH, in which R has the aforesaid meaning, withthionyl chloride to obtain the corresponding acyl chloride;

(b) esterifying ephedrine (II) with RCOCl, in which R has the aforesaidmeaning, to obtain the ester (III): ##STR5##

(c) condensing the tricyclic derivative (IV), in which X is a halogen,with the ester (III): ##STR6## In those cases in which in addition tothe carboxyl group other functional groups such as OH or NH₂ are bondedto the radical R, these functional groups are preferably firstlyprotected, and the condensation reaction is conducted preferably withthe acid protected in this manner without passing through the acylchloride.

Reaction (a) is conducted by treating the acid RCOOH with thionylchloride at a temperature of between 30° and 50° C.

Reaction (b) is conducted by slowly adding the acyl chloride to theephedrine at a temperature maintained between 2° C. and 8° C. and in thepresence of an acid acceptor such as triethylamine or pyridine, thistemperature then being maintained for 5-20 hours.

Alternatively, in the case of more reactive acyl chlorides, theprocedure can be conducted in a solvent such as acetone ormethylethylketone in the presence of sodium carbonate at a temperatureof between 40° C. and the boiling point.

Reaction (c) is conducted in a reaction medium consisting of an organicsolvent boiling under reflux in the present of an acid acceptor, andpreferably in the presence of sodium bicarbonate.

Acetonitrile is preferably used as the organic solvent.

In the tricyclic derivative (IV), X is preferably Cl.

If the RCOOH acids contain functional hydroxyl groups, these groups areprotected by esterification, preferably by the formation of the acetate,which is then reacted with the ephedrine (III), preferably by thedehydration method using dicyclohexylcarbodiimide (DCC) which incontrast to the acyl chloride method enables the hydroxyl protectiongroup to be kept integral. This group is hydrolysed under mildconditions after reaction (c).

If the RCOOH acids contain functional amino groups, these are protectedby t-butyloxycarbonyl (BOC) groups.

In these cases the reaction with ephedrine (III) is again preferablyconducted by the dehydration method using dicyclohexylcarbodiimide (DOC)and the protection group is hydrolysed after reaction (c).

PHARMACOLOGICAL TRIALS

Those derivatives of the invention coded ET 2001, ET 2002, ET 2003 andET 2004, as prepared in accordance with Examples 1, 2, 3 and 4respectively, were tested in pharmacological trials to determine theiracute toxicity and their antiulcer activity on ulcers induced byligature of the pylorus and on ulcers induced by cold stress.

For comparison purposes the same trials were carried out using theproduct WAS 4304 described in European patent application No.84108424.7.

1. ACUTE TOXICITY

Acute toxicity was determined on Swiss albino mice having an averageweight of about 20 grams and on Wistar rats having an average weight of150±10 grams by endoperitoneal administration. All animals were keptfasting for 12 hours before the trial. For the trial, 10 animals, namely5 males and 5 females, were used for each dose level.

The LD₅₀ values, expressed as mg/kg, are calculated on the basis of themortality determined within eight days from administration, inaccordance with the Lichtfield and Wilcoxon method. The results aregiven in the following Table 1.

                  TABLE 1                                                         ______________________________________                                        LD.sub.50 in the mouse and rat                                                               LD.sub.50 mg/kg                                                Type of                                                                              Method of   WAS     ET    ET    ET   ET                                animal administration                                                                            4304    2001  2002  2003 2004                              ______________________________________                                        Mouse  endoperitoneal                                                                            127     585   535   580  630                               Rat    endoperitoneal                                                                            87      510   590   618  681                               ______________________________________                                    

2. ANTIULCER ACTIVITY against ulcers induced by ligature of the pylorus(Shay test): Groups of 10 Sprague Dawley rats of body weight between 200and 250 grams were placed in cages under conditions of standardtemperature (21°±2° C.), standard relative humidity (60-70%) andstandard light (12 hours per day).

The animals were fed with rat pellets and with water at will.

The derivatives to be tested were administered orally 6, 12, 24 and 36hours before ligature of the pylorus, after dispersion in physiologicalsolution using Tween 80 as dispersant in a quantity of 1% andcarboxymethylcellulose in a quantity of 0.2%. The volume administeredwas 10 ml/kg.

Before ligature, the rats had been kept without food for 18 hours butwith free access to water, the pylorus ligature then being made underether anesthetic, with suture of the peritoneum and of the abdominalwall.

The animals were then kept without food or water, and 18 hours afterligature were sacrificed using chloroform, their stomachs then beingwithdrawn and opened along the small curvature.

The gastric surface was extended to observe the ulcers, the evaluationbeing made by measuring their maximum width.

Table 2 shows the results obtained by administering the variousderivatives at various times before ligature of the pylorus.

                  TABLE 2                                                         ______________________________________                                        Antiulcer activity against ulcers induced by ligature                         of the pylorus                                                                             ED.sub.50 mg/kg by oral administration at                        Active       various times before pylorus ligature                            principle    6 h     12 h     24 h   36 h                                     ______________________________________                                        WAS 4304     0.2     1.1      1.8    2.4                                      ET 2001      0.5     0.5*     0.7*   1.3*                                     ET 2002      0.4     0.5*     0.8*   1.1*                                     ET 2003      0.4     0.4*     0.7*   1.2*                                     ET 2004      0.5     0.4*     0.6*   1*                                       ______________________________________                                         *P < 0.05 ED.sub.50 values of ET 2001, ET 2002, ET 2003, ET 2004 versus       WAS 4303 at the same times of administration.                            

3. ANTIULCER ACTIVITY against ulcers induced by cold stress: This trialwas carried out on Wistar rats weighing about 300 grams each.

The animals were divided randomly into groups of 10 animals each andkept without food for 18 hours before the trial, but had unrestrictedwater.

The active principles were administered to the animals orally in theform of a physiological solution which also contained 1% of Tween 80 and0.2% of carboxymethylcellulose, one hour before securing to a laboratoryboard.

After ligature, the animals were placed in a refrigerator at atemperature of between 2° C. and 4° C. for two hours.

After this time the rats were sacrificed, their stomachs were withdrawnand opened along the small curvature, and the gastric mucosa checked.

The number of ulcers was counted and their relative diameters measured.From these individual data the mean value for each treatment group wasobtained and the inhibition capacity calculated as a percentage relativeto the control group, using the following formula: ##EQU1## where C isthe mean value in mm for the control group and T the mean value for thegroup treated with the derivative under examination.

Table 3 shows the results obtained by administering the derivativesunder examination at different times before subjection to cold stress.

                  TABLE 3                                                         ______________________________________                                        Antiulcer activitiy against ulcers induced by cold stress                                  ED.sub.50 mg/kg by oral administration at                                     various times before commencement                                Active        of cold stress                                                  principle    6 h     12 h     24 h   36 h                                     ______________________________________                                        WAS 4304     0.4     1.6      2.5    2.8                                      ET 2001      0.4     0.9*     1.2*   2.1*                                     ET 2002      0.7     1*       1.4*   1.9*                                     ET 2003      0.6     0.9*     1.3*   1.7*                                     ET 2004      0.6     0.8*     1.4*   1.8*                                     ______________________________________                                         *P < 0.05 ED.sub.50 values of ET 2001, ET 2002, ET 2003, ET 2004 versus       WAS 4303 at the same times of administration.                            

DISCUSSION OF RESULTS

From Table 1 it can be seen that the LD₅₀ of the derivatives accordingto the invention is decidedly higher than that of WAS 4304.

From Tables 2 and 3 it can be seen that the ED₅₀ of the derivativesaccording to the invention is similar to that of WAS 4304 foradministration 6 hours before commencement of the trial, whereas it isdecidedly lower for administration 12, 24 and 36 hours beforecommencement of the trial.

Thus the derivatives according to the invention have lower toxicity andmuch more prolonged antiulcer activity than WAS 4304.

The long duration of action is very important in the treatment ofgastric and/or duodenal ulcer because it enables gastric secretion to becarried to its physiological limits without incurring periods ofachlorhydria because of hyperdosage, or secretion rebound because ofunderdosage.

It also simplifies chronic ingestion of the medicament; in this respectthe administration of a medicament at a dosage rate of once or twiceevery two days is particularly well accepted by the patient and alsoenables a more personalized and precise treatment plan to be establishedfor each patient.

The following examples of the preparation of the four derivatives usedin the pharmacological trials are described for illustrative purposesonly and have no limiting effect.

EXAMPLE 1 Preparation of (I) where R=C₉ H₁₉ (derivative ET 2001)

The chloride of decanoic acid is prepared by reacting the acid (17.2 g,0.1 mole) in thionyl chloride (23.8 g, 0.2 moles), heating the reactionmixture to 40° C. for 4 hours. The excess thionyl chloride is distilledoff, followed by the acid chloride, which is reacted directly withephedrine in the following manner: basic ephedrine (16.5 g, 0.1 mole)and pyridine (50 ml) are placed in a flask cooled with external ice, andthe decanoic acid chloride (20 g, 0.106 moles) is added very slowly. Themixture is left at 5° C. for 12 hours, after which iced water is addedslowly to precipitate the chloride of the ephedrine ester (23 g, 65%),which can be recrystallised from isopropyl ether, M.P. 100°-104° C.

    ______________________________________                                        Elementary analysis for C.sub.20 H.sub.34 NO.sub.2 Cl                         calculated  C 67.5%    H 9.6%     N 3.9%                                      found       C 67.75%   H 9.8%     N 4.1%                                      ______________________________________                                    

This ester is reacted with an equimolar quantity of the tricycliccompound (IV) in 400 ml of acetonitrile in the presence of 10 g ofNaHCO₃ under boiling reflux conditions for 6 hours.

The product obtained is filtered and crystallised from acetonitrile witha yield of 54%.

EXAMPLE 2 Preparation of (I) where ##STR7## (derivative ET 2002)

Basic ephedrine (16.5 g, 0.1 mole) and DCC (20.6 g, 0.1 mole) are addedat ambient temperature (18° C.) to a solution oft-butyloxy-carbonyl-histidine (25.5 g, 0.1 mole) in a mixture of ethylacetate-dioxane (3:1, 100 ml). A mixture of ethyl acetate:hexane (2:1)is added and the dicyclohexylurea which forms is filtered off.

The formed ester is crystallised twice from methylene chloride-methanol,M.P. 148°-150° C.

    ______________________________________                                        Elementary analysis for C.sub.21 H.sub.30 N.sub.4 O.sub.4 C                   calculated  C 62.7%    H 7.5%     N 13.9%                                     found:      C 62.9%    H 7.7%     N 14.0%                                     ______________________________________                                    

The ester prepared in this manner is reacted with the tricyclic compound(IV) under conditions analogous to Example 1, and only after thisreaction the t-butyloxycarbonyl group is hydrolysed with trifluoroaceticacid at ambient temperature.

EXAMPLE 3 Preparation of (I) where ##STR8## (derivative ET 2003)

Nicotinic acid chloride hydrochloride is prepared by reacting the acid(12 g, 0.1 mole) in thionyl chloride (23.8 g, 0.2 moles) by heating to40° C. for 8 hours. The acid chloride hydrochloride is filtered off andis reacted directly with ephedrine in the following manner: basicephedrine (16.5 g, 0.1 mole) and pyridine (50 ml) are placed in a flaskcooled with external ice, and the nicotinic acid chloride hydrochloride(18.8 g, 0.106 moles) is added very slowly. The mixture is left for 12hours at 5° C., after which iced water is slowly added to precipitatethe ephedrine ester hydrochloride (20 g, 65%), which can berecrystallised from methanol/isopropyl ether. M.P. 172°-174° C.

    ______________________________________                                        Elementary analysis for C.sub.16 H.sub.19 N.sub.2 O.sub.2                     calculated  C 62.2%    H 6.2%     N 9.1%                                      found       C 62.85%   H 6.4%     N 9.3%                                      ______________________________________                                    

This ester can be reacted with the tricyclic compound (IV) underconditions analogous to Example 1, with a yield of 58%.

EXAMPLE 4 Preparation of (I) where ##STR9## (derivative ET 2004)

The preparation is analogous to the preparation of Example 3.

I claim:
 1. Esterified ephedrine derivatives of general formula:##STR10## wherein R is selected from the group consisting of: ##STR11##2. Pharmaceutical compositions comprising an anti-ulcer effective amountof a compound of claim 1 and a therapeutically acceptable carrier.